Geology

Costa Rica Guide

Geology

Costa Rica is a naturally formed volcanic land bridge between North and South America. Part of the Ring of Fire, there are several active volcanoes within the country's borders. It is truly a geologist's dreamland, as many of these volcanoes have roads that take tourists right to their rims.

It is believed that Costa Rica was formed quickly, taking only 50 million years to appear, and appearing a mere 3 million years ago. Two of Earth's major plates, the Cocos and the Caribbean, are responsible for the movement that created this land. Continuing movements in the plates over the years is visible in the distance between the mainland and islands that are now far out to sea.

Volcanoes do a great job of creating rich soil, and that has led to an incredible biodiversity. There are 6 classified active volcanoes and 60 classified dormant in the country. Costa Rica hosts as much as 10% of Earth's biodiversity! It must be true that greatness is born from the furnaces!

Nicoya Peninsula

The northwest coast of Costa Rica is situated directly above the subduction zone. Cocos plate is being overtaken by the Caribbean plate, and active times are close at hand. Earthquakes are the primary concern for this region. In 1950 there was a 7.7 and in 2012 there was a 7.6 with an epicenter only 12 km offshore. Public outreach and education regarding the possibility of these quakes saved innumerable lives, and only two people died in the 2012 event.

The end of the Middle America Trench is situated just off the coast of the Nicoya Peninsula. It goes to depths of over 21,000 feet and is seen as a rapid point of subduction in plate tectonic terminology. With a blazing fast average movement of 9 cm per year, it is no wonder the triggered earthquakes are referred to as megathrust.

Volcanoes: Active and Extinct

The last major volcanic eruption in Costa Rica took place in 1910. Poas Volcano is anything but dormant, though, as visitors frequently report seeing geysers explode out of the craters. The highest measured in the last 100 years has been over 800 feet. These are not lava eruptions, but acidic lakes of captured rainwater venting sulfuric gases. Evacuations have been mandatory because of the severity of some of these occasions. It is 8885 feet high. Irazu Volcano is Costa Rica's highest, at 11,260 feet. Both of these are located in the Central Highlands.

Guanacaste, the northwestern region in Costa Rica, is home to some of the most recent volcanic activity in the country. Rincon de la Vieja National Park holds nine craters, including the Santa Maria Volcano. A hike up this difficult peak rewards achievers with stunning vistas of the surrounding terrain. Tenorino Volcano offers another unique hiking experience in this region. Each of these mountains is less than 6300 feet in altitude, but difficult to champion.

Costa Rica's most famous volcano, Arenal, is located in the north central region of Alajuela. It erupted back to life in 1968, killing 87 people and caused major disruption to towns of Pueblo Nuevo and Tabacon. Consistent lava flows called innumerable tourists to the area until 2010 when a significant decline in activity occurred. The mountain is still classified as active, some placing it in the top 10 most active in the world.

Tropical Forest Soil

Costa Rica is a relatively young landmass. It has only been fully formed, according to volcanic dating, for roughly 3 million years. Over that timeframe, several eruptions per century have continued to add to the topsoil and terrain. According to the pH balances, it is no wonder the biodiversity here is so great as compared to other tropical climates. Higher acidity in older soil keeps growing options more limited, but soils in Costa Rica are closer to neutral, comprised of inceptisols and entisols. These are of a much richer organic quality, carrying more minerals near the surface than ultisols. These rich soils are also found higher in elevation than in other tropical locations, creating "cloudforests." Richly diverse flora and fauna covered lands are rarely found so high up mountains as in Costa Rica.